The present invention relates to a video camera apparatus using an imager and, more particularly, is directed to a video camera apparatus having a function to electronically correct an image vibration caused by a handling or the like.
Recently, with the progress of semiconductor technologies, video camera apparatus have been more and more miniaturized and made light-weight. Concurrently therewith, a very small vibration of a reproduced picture due to a handling or the like becomes conspicuous when a picked-up video signal is reproduced.
To solve the aforesaid problems, the technology for correcting an image vibration caused by a handling or the like has been proposed, in which a video camera apparatus includes a vibration detector for detecting an image vibration caused by a handling or the like and an image vibration caused by a handling or the like can be corrected by mechanically moving an optical lens or moving a scanning area of an imager within a photo-sensitive pixel area on the basis of a detected signal from this vibration detector (see paper "VHS CAMCODER WITH ELECTRONIC IMAGE STABILIZER written by OHIMA et al. on IEEE Trans. on CE Vol. 35, No. 4 (Nov. 1989) pp. 749-757).
In the system for correcting an image vibration caused by a handling or the like by moving the scanning area of the imager within the photo-sensitive pixel area on the basis of the detected output from the above-mentioned vibration detector, signals of adjacent horizontal scanning lines (hereinafter simply referred to as adjacent 2H signals) are respectively multiplied by .alpha. times (where 0.ltoreq..alpha..ltoreq.1) and 1-.alpha. times and then added by an interpolation processing circuit, whereby the scanning area is moved equivalently. A linear interpolation processing will be described with reference to FIG. 1.
In FIG. 1 of the accompanying drawings, reference symbols a, b and c depict pixel signals of adjacent horizontal scanning lines, and reference symbol .alpha. depicts a coefficient used in the interpolation processing, i.e., interpolation coefficient. Also, reference symbols D.sub.1, D.sub.2, . . . , depict signals that are generated by the interpolation processing, respectively. The signals D.sub.1, D.sub.2 are obtained by the following equations (1) and (2) when the signals a and b and the signals b and c are taken as adjacent 2H pixel signals, respectively: EQU D.sub.1 =(1-.alpha.).multidot.a+.alpha..multidot.b (1) EQU D.sub.2 =(1-.alpha.).multidot.b+.alpha..multidot.c (2)
In the above equation (1), when .alpha. is 0, then D.sub.1 =a. When .alpha.=1, then D.sub.1 =b. Also, in the above equation (2), when .alpha.=0, D.sub.2 =b. When .alpha.=1, then D.sub.2 =c.
To correct horizontal and vertical image vibrations caused by the handling or the like, an amount that the scanning area of the imager is moved within the photo-sensitive pixel area in response to the detected signal from the vibration detector must be calculated. Further, to move this scanning area within the photo-sensitive pixel area by the calculated moving amount, the scanning area cannot be moved at the unit smaller than the pixel unit only by controlling the scanning pulse that drives the imager. However, by using the above-mentioned interpolation coefficient .alpha. used in the interpolation processing, the scanning area can be moved at the pitch smaller than the pixel unit within the photo-sensitive pixel area.
According to the above-mentioned interpolation processing, if the pixel signal D.sub.1 is obtained by interpolating the pixel signals a and b, then the pixel signal D.sub.1 can be regarded as the pixel signal located on a scanning line that is assumed to be shifted from the scanning line of the pixel signal a to the scanning line of the pixel signal b by a shift amount .alpha.L where L represents an interval between the adjacent two scanning lines. In other words, the above operation becomes equivalent to the operation that the scanning area is moved by the amount .alpha.L.
Incidentally, when the interpolation coefficient .alpha. used in the interpolation processing is changed with the movement of the scanning area, there is then the problem that a resolution of a reproduced picture is deteriorated depending on the value of the interpolation coefficient .alpha..
FIG. 2 shows measured results obtained when a resolution of a picture processed by the interpolation processing is changed relative to the change of the interpolation coefficient .alpha.. Study of FIG. 2 reveals that a resolution of a reproduced picture is deteriorated as the interpolation coefficient .alpha. approaches 1/2, i.e., the signal that results from processing the adjacent 2H signals by the interpolation processing approaches a signal on the scanning line that is assumed to be located at the intermediate position of the two horizontal scanning lines. Especially, the deterioration of the resolution of the reproduced picture except areas 0&lt;.alpha.&lt;1/4 and 3/4&lt;.alpha.&lt;1 shown hatched in FIG. 2 is remarkable.